Cooling System

ABSTRACT

A cooling system provided with a first freezing circuit which comprises a first compressor, a first condenser, a first expansion mechanism and a first heat exchanger and in which a first refrigerant is circulated; a second freezing circuit which comprises a second compressor, a second heat exchanger, a second expansion mechanism and an evaporator and in which a second refrigerant is circulated; and a heat medium circuit in which a heat medium for exchanging heat between the first refrigerant of the first heat exchanger and the second refrigerant of the second heat exchanger is circulated, wherein the first freezing circuit is arranged on the exterior side and the second freezing circuit is arranged in the machinery room of a thermal system on the interior side.

BACKGROUND OF THE INVENTION

(i) Field of the Invention

The present invention relates to a cooling system for use in airconditioning systems, freezers, refrigerators, refrigerated showcasesand the like.

(ii) Description of the Related Art

Previously, the refrigerant generally used in cooling systems for use inair conditioning systems, freezers, refrigerators, refrigeratedshowcases and the like was chlorofluorocarbon (CFC). However, thedepletion of the ozone layer surrounding the earth by CFC has posed anenvironmental problem. To address this problem, cooling systems using anatural refrigerant, such as ammonia or carbon dioxide, as analternative to CFC have come into use in recent years. Known suchcooling systems include, for instance, a unified cooling system having acompressor, a condenser, an expansion valve and an evaporator which areinstalled in a refrigerated showcase, but such a unified cooling systemis poor in freezing efficiency.

In this connection, as a solution to the problem with the unifiedcooling system, there are known a cooling system shown in FIG. 3 and adual cooling system shown in FIG. 4.

Each of the cooling systems shown in FIG. 3 and FIG. 4 is configured ofan ammonia circuit 51 and a carbon dioxide circuit 52. The ammoniacircuit 51 is further provided with a compressor 51 a, a condenser 51 b,an expansion valve 51 c and an external heat exchanger 53. Therefrigerant used by the ammonia circuit 51 is ammonia. The carbondioxide circuit 52 is further provided with a compressor 52 a, anexpansion valve 52 b, an evaporator 52 c and the external heat exchanger53. The refrigerant used by the carbon dioxide circuit 52 is carbondioxide. The compressor 52 a and the external heat exchanger 53 areconnected to each other by piping 53 a, and the expansion valve 52 b andthe external heat exchanger 53 are connected to each other by piping 53b.

The cooling system shown in FIG. 3, configured in this way, has thecompressor 52 a, the expansion valve 52 b and the evaporator 52 carranged in a refrigerated showcase C arranged on an interior A side(indicated by double-dot chain lines in FIG. 3). The cooling systemshown in FIG. 4 has the expansion valve 52 b and the evaporator 52 c ina refrigerated showcase C arranged on the interior A side (indicated bydouble-dot chain lines in FIG. 4). Further, each of the cooling systemsshown in FIG. 3 and FIG. 4 has the ammonia circuit 51 on an exterior Bside.

However, each of the cooling systems shown in FIG. 3 and FIG. 4 has thepiping 53 a within which a high-temperature high-pressure refrigerantflows or the piping 53 b within which a high-pressure refrigerant flowsarranged in the state of being exposed on the interior A. Thearrangement of the piping 53 a and the piping 53 b arranged in the stateof being exposed on the interior A makes the cooling systems shown inFIG. 3 and FIG. 4 subject to the fear of allowing the refrigerant toleak out indoors.

Also, in each of the cooling systems shown in FIG. 3 and FIG. 4 may needlong-extended piping 53 a or 53 b depending on the location of therefrigerated showcase C placed on the interior A side. Where the piping53 a or 53 b is long, the required quantity of the refrigerant to besealed in increases correspondingly. Therefore, in the cooling systemshown in FIG. 3 and FIG. 4, if the high-pressure refrigerant leaks tothe interior A, a large quantity of the refrigerant may leak out to theinterior A.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a safe cooling systemwhich can prevent its refrigerant from leaking into the room (except themachinery room for the indoor unit of the thermal system).

In order to achieve the object stated above, the cooling systemaccording to the invention is provided with a first freezing circuitwhich comprises a first compressor, a first condenser, a first expansionmechanism and a first heat exchanger and in which a first refrigerant iscirculated; a second freezing circuit which comprises a secondcompressor, a second heat exchanger, a second expansion mechanism and anevaporator and in which a second refrigerant is circulated; and a heatmedium circuit in which a heat medium for exchanging heat between thefirst refrigerant of the first heat exchanger and the second refrigerantof the second heat exchanger is circulated, wherein the first freezingcircuit is arranged on the exterior side and the second freezing circuitis arranged in the machinery room of a thermal system on the interiorside.

This cooling system has its first freezing circuit in which thehigh-pressure first refrigerant circulates installed on the exteriorside. The cooling system has its second freezing circuit in which thehigh-pressure second refrigerant circulates installed in the machineryroom of a thermal system arranged on the interior side. The arrangementof the first freezing circuit on the exterior side and of the secondfreezing circuit in the machinery room means the interior arrangement ofno piping in which the high-pressure first refrigerant or thehigh-pressure second refrigerant flows (except the piping in themachinery room of the thermal system). This means enhanced safetybecause there is no fear of leaking of the high-pressure firstrefrigerant or the high-pressure second refrigerant into the room.Furthermore, this cooling system has a heat medium circuit interveningbetween the first freezing circuit and the second freezing circuit. Thisheat medium circuit enables heat to be exchanged between the firstrefrigerant of the first freezing circuit and the second refrigerant ofthe second freezing circuit. The intervening presence of the heat mediumcircuit makes it unnecessary to elongate the piping of the firstfreezing circuit or of the second freezing circuit even if the machineryroom of the thermal system is installed rather far from the exteriorside. Therefore, the required quantity of the first refrigerant or thesecond refrigerant can be minimized and accordingly the safety ofoperation can be enhanced.

The above-stated objects and other objects, features and advantages ofthe invention will become more apparent from the following descriptionwhen taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic configuration of a cooling system of a firstpreferred embodiment of the present invention;

FIG. 2 shows a schematic configuration of a cooling system of a secondpreferred embodiment of the invention;

FIG. 3 shows a schematic configuration of a conventional cooling system;and

FIG. 4 shows a schematic configuration of another conventional coolingsystem.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a first preferred embodiment of the invention.

This cooling system comprises a first freezing circuit 10, a secondfreezing circuit 20 and a heat medium circuit 30.

The first freezing circuit 10 is provided with a first compressor 11, afirst condenser 12, a first expansion valve 13, which is a firstexpansion mechanism, and a first heat exchanger 14. This first freezingcircuit 10 circulates a first refrigerant in the sequence of the firstcompressor 11→the first condenser 12→the first expansion valve 13→thefirst heat exchanger 14→the first compressor 11. The first refrigerantused in the first freezing circuit 10 is a natural refrigerant (e.g.,ammonia).

The second freezing circuit 20 is provided with a second compressor 21,a second heat exchanger 22, a second expansion valve 23, which is asecond expansion mechanism, and an evaporator 24. This second freezingcircuit 20 circulates a second refrigerant in the sequence of the secondcompressor 21→the second heat exchanger 22→the second expansion valve23→the evaporator 24→the second compressor 21. The second refrigerantused in the second freezing circuit 20 is the natural refrigerant (e.g.,carbon dioxide).

The heat medium circuit 30 is provided with the first heat exchanger 14,the second heat exchanger 22 and a circulating pump 31. The first heatexchanger 14 is shared by the first freezing circuit 10 and the heatmedium circuit 30. The second heat exchanger 22 is shared by the secondfreezing circuit 20 and the heat medium circuit 30. The heat mediumcircuit 30 circulates a heat medium in the sequence of the first heatexchanger 14→the circulating pump 31→the second heat exchanger 22→thefirst heat exchanger 14. The heat medium used in this heat mediumcircuit 30 is brine (e.g., a calcium chloride solution) or water.

The cooling system configured as described has the first freezingcircuit 10 and the first heat exchanger 14 installed on an exterior Bside. Further, the cooling system has the second freezing circuit 20 andthe second heat exchanger 22 installed in a machinery room of arefrigerated showcase C, which is a thermal system arranged on aninterior A (indicated by double-dot chain lines in FIG. 1) side.

Next, the operation of the cooling system shown in FIG. 1 will bedescribed.

The first refrigerant of the first freezing circuit 10 circulates in thesequence of the first compressor 11→the first condenser 12→the firstexpansion valve 13→the first heat exchanger 14→the first compressor 11(see the broken arrow in FIG. 1). The second refrigerant of the secondfreezing circuit 20 circulates in the sequence of the second compressor21→the second heat exchanger 22→the second expansion valve 23→theevaporator 24→the second compressor 21 (see the solid arrow in FIG. 1).Further, the heat medium of the heat medium circuit 30 circulates in thesequence of the first heat exchanger 14→the circulating pump 31→thesecond heat exchanger 22→the first heat exchanger 14 (see the bold arrowin FIG. 1). The circulation of the first refrigerant, the secondrefrigerant or the heat medium in the circuit 10, 20 or 30, respectivelycauses heat to be exchanged in the first heat exchanger 14 between thefirst refrigerant flowing in the first freezing circuit 10 and the heatmedium flowing in the heat medium circuit 30 or, in the second heatexchanger 22, between the second refrigerant flowing in the secondfreezing circuit 20 and the heat medium flowing in the heat mediumcircuit 30. These heat exchanges cause the refrigerated showcase Carranged on the interior A side to be refrigerated by the cooled secondrefrigerant.

In the cooling system of this embodiment, the first freezing circuit 10in which the high-pressure first refrigerant circulates is arrangedoutside the room, and the second freezing circuit 20 in which thehigh-pressure second refrigerant circulates is arranged inside therefrigerated showcase C. This arrangement prevents the piping in whichthe high-pressure first refrigerant or the second refrigerant flows frombeing placed on the interior A side (except the piping in the machineryroom of the refrigerated showcase C). Therefore, the cooling system ofthis embodiment can be enhanced in safety because there is no fear ofleaking of the high-pressure first refrigerant or second refrigerantinto the room.

Further in the cooling system of this embodiment, the heat mediumcircuit 30 intervenes between the first freezing circuit 10 and thesecond freezing circuit 20. This makes it unnecessary to elongate thepiping of the first freezing circuit 10 or of the second freezingcircuit 20 even if the refrigerated showcase C is installed rather farfrom the exterior B. Therefore, the cooling system of this embodimentcan serve to minimize the required quantity of the first refrigerant orthe second refrigerant and accordingly to enhance the safety ofoperation.

FIG. 2 shows a second embodiment of the invention. The same constituentparts as those in the cooling system 1 shown in FIG. 1 are representedby respectively the sane reference numerals and their description willbe dispensed with.

The cooling system shown in FIG. 2 differs from the cooling system shownin FIG. 1 in that a heat medium circuit 40 is a known thermo-siphon typecircuit using natural convection.

The cooling system shown in FIG. 2 also differs from the cooling systemshown in FIG. 1 in that a low-pressure working fluid is used as the heatmedium for the heat medium circuit 40.

The heat medium circuit 40 comprises the first heat exchanger 14 and thesecond heat exchanger 22. Thus, the first heat exchanger 14 is shared bythe first freezing circuit 10 and the heat medium circuit 40, and thesecond heat exchanger 22 is shared by the second freezing circuit 20 andthe heat medium circuit 40. Further, since a thermo-siphon type circuitis used as the heat medium circuit 40, the heat medium circuit 40circulates the low-pressure working fluid in the sequence of the firstheat exchanger 14→the second heat exchanger 22→the first heat exchanger14 by utilizing natural convection. The working fluid used in this heatmedium circuit 30 is a low-pressure refrigerant (e.g., water oralcohol).

The cooling system configured as described above has the first freezingcircuit 10 and the first heat exchanger 14 installed on the exterior Bside. Further, the cooling system has the second freezing circuit 20 andthe second heat exchanger 22 installed in the machinery room of therefrigerated showcase C, which is the thermal system arranged on theinterior A (indicated by double-dot chain lines in FIG. 2) side.

Next, the operation of the cooling system shown in FIG. 2 will bedescribed.

As the circulation of the first refrigerant in the first freezingcircuit 10 and that of the second refrigerant in the second freezingcircuit 20 are the same as in the first embodiment described above,their description will be dispensed with. The working fluid of the heatmedium circuit 40 circulates in the sequence of the first heat exchanger14→the second heat exchanger 22→the first heat exchanger 14 (see thebold arrow in FIG. 2). The circulation of the first refrigerant, thesecond refrigerant or the working fluid in the circuit 10, 20 or 40respectively causes heat to be exchanged in the first heat exchanger 14between the first refrigerant flowing in the first freezing circuit 10and the low-pressure working fluid flowing in the heat medium circuit 40and in the second heat exchanger 22 between the second refrigerantflowing in the second freezing circuit 20 and the low-pressure workingfluid flowing in the heat medium circuit 40. These heat exchanges causethe refrigerated showcase C arranged on the interior A side to berefrigerated by the cooled second refrigerant.

In the cooling system of this embodiment, the working fluid flowing inthe heat medium circuit 40 arranged on the interior A side is low inpressure. The low pressure of the working fluid means that the coolingsystem of this embodiment has no high-pressure piping on the interior Aside, resulting in enhanced safety. The other effects and advantages ofthe cooling system shown in FIG. 2 are the same as those of the coolingsystem shown in FIG. 1.

In the first and second embodiments described above, the second freezingcircuit 20 and the second heat exchanger 22 are arranged in therefrigerated showcase C, which is a machinery room, but this is not theonly possible arrangement. For instance, the second freezing circuit 20and the second heat exchanger 22 may as well be arranged within an airconditioning system, a freezer or a refrigerator, which is a thermalsystem.

The preferred embodiments described in this specification are onlyillustrative but not limiting. The scope of the invention is stated inthe appended claims, and all the variations that can be covered by themeanings of those claims are included in the present invention.

1. A cooling system comprising: a first freezing circuit which comprisesa first compressor, a first condenser, a first expansion mechanism and afirst heat exchanger and in which a first refrigerant is circulated; asecond freezing circuit which comprises a second compressor, a secondheat exchanger, a second expansion mechanism and an evaporator and inwhich a second refrigerant is circulated; and a heat medium circuit inwhich a heat medium for exchanging heat between the first refrigerant ofthe first heat exchanger and the second refrigerant of the second heatexchanger is circulated, wherein: the first freezing circuit is arrangedon a exterior side and the second freezing circuit is arranged in amachinery room of a thermal system on a interior side.
 2. The coolingsystem according to claim 1, wherein the heat medium circuit is soconfigured that the heat medium is circulated between the first heatexchanger and the second heat exchanger with a pump.
 3. The coolingsystem according to claim 1, wherein the heat medium circuit is soconfigured that the heat medium is circulated between the first heatexchanger and the second heat exchanger with a thermo-siphon.
 4. Thecooling system according to claim 1, wherein the first refrigerant isammonia.
 5. The cooling system according to claim 1, wherein the secondrefrigerant is carbon dioxide.